Transformer



June 14, 1949.

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51+ PAUL BERGER Attorney Patented June 14, 1949 TRANSFORMER Paul Berger, Chicago, Ill., asslgnor, by mesne assignments, of one-half to Hirsch Epstein and one-half to Louis R. Duman, both of Chicago, Ill.

Application January 26, 1946, Serial No. 643,664

7 Claims. (Cl. 323-44) This invention relates to electric transformers for hot cathode glow discharge lamps.

Transformers of the type of the present invention are designed generally to operate a plurality of lamps through a circuit including a condenser in series with one of the lamps to cause it to take the leading current to correct for the lagging current taken by the other lamp.

In operating a pair of fluorescent tube lamps from separate secondaries of a unitary transformer trouble has been encountered when the leading lamp is in operation and the starter circuit closed to heat the filaments of the lagging lamp. This trouble has been due primarily to the mutual reactance between the two secondaries which aflects the already operating leading lamp and reduces the voltage, sometimes to the point resulting extlnguishment of the operating lamp. It is one of the objects of the present invention to provide a transformer having separate secondaries for supplying current to a leading and a lagging glow discharge lamp and wherein the arrangement is such that the leakage reactance caused by the starting of one lamp will not have an objectionable effect on the other lamp. 7

In the preferred form of the present invention the transformer core is made up of two stacks of L-shaped laminations arranged to form 9, rectangle, with 'two longitudinal sides thereof each containing a pair of primary windings and a secondary winding between the pair of primary windings. The four primary windings on-the core are connected in series to have a cumulative effect. The secondary windings supply energy to the respective lamps. Each of the primary cells is made of a length very much less than the length of the secondary coil. In one installation each primary coil was approximately one-third the length of the secondary. The secondary coils are made much longer than the primary coils.

In some fluorescent lighting transformers of the above mentioned type intended for supplying current to one leading lamp and one lagging lamp difllculty has been encountered if one of the two lamps is out of service. This difllculty has been due to the fact thatthe operating lamp may carry an excessive current to the detriment of the operating lamp. 'By the present arrangement, due to the fact that the coupling between the secondaries is decreased, there is a diminution of the tendency for the current to rise in the leading lamp when the lagging lamp i out 0! service. This diminution may be further accentuated by providing auxiliary coils in series with the secondaries of the lagging lamp, which auxiliary coils are located on the transformer core in a position to generate'a counter E. M. F. in the secondary circuit to inhibit the rise of current in the secondary circuit of the other lamp. A similar result may be obtained by means of a magnetic shunt across the core to prevent an excessive flux from passing through either secondary coil when the other secondary coil is' connected to a defective lamp.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawings form-.

ing a part thereof.

In the drawings:

Figure 1 illustrates a transformer of the present invention connected to a pair of fluorescent glow discharge lamps;

Figure 2 illustrates a transformer which is a modification of the transformer of Figure l; and

Figure 3 shows another modification.

In the various figures like reference numerals designate like parts throughout.

Reference may now be had more particularly to the embodiment illustrated in Figure 1. The transformer l of Figure 1 comprises an iron core formed of two similar stacks of L-shaped laminations, indicated at 2 and 3. The stacks 2 and ,3 are in magnetic abutment at 4 and 5. On each of the long legs of the two core sections there are located two primary coils, namely, a

pair of primary coils 61 on one leg and a pair of coils 8-9 on the other leg, all four coils being connected in series. Between the coils :6

and I there is located a secondary coil l0, and

between the coils 8 and 9 there is located a secondary coil II. The primary coils are connected in series directly across line conductors 14-45 which may lead to any suitable source of alternating current, say, a cycle' volt source.' The secondary coil i0 is connected to one side of the primary coils to constitute a step-up autotransformer to supply current to a hot cathode fluorescent type glow discharge lamp l6. In a like manner the secondary II i connected to one side of the primary coils to constitute a step-up auto-transformer to supply current through a .condenser I! to a hot cathode glow discharge fluorescent type lamp l8. Each of the lamps is provided with a pair 0! heating:

filaments that are adapted to be connected together in series by means of a conventional starter switch 8- which opens the circuit after a:

time interval, allowing the cathodes to become sufiiciently hot to permit arc formation through the ionized gases within the tube, in a manner well known in the art.

In one type of transformer of the present invention the laminated iron core 8 was 1% inches wide and 8% inches long and approximately of an inch thick. Each of the primary coils contained approximately 530 turns and was of a length of approximately 11% inches. The coil l had approximately 2050 turns whereas the coil Ii had approximately 1700 turns. Each one of the secondary coils was of a length oi approximately 4% inches. I have found that in such a transformer the spacing between the secondary H and each of its adjacent primaries can be varied from zero to /2 inch without seriously affecting the characteristics of the transformer. I

The entire transformer was enclosed in a magnetic casing with the coils resting on the bottom of the casing and one end of the transformer approximately /2 inch from the end of the casing and the other end a number of inches from the end of the casing to allow space for the condenser Ill. A magnetic cover closed the casing, said cover overlaying the coils. The entire space within the casing. which was not occupied by the transformer and condenser, was filled with a tar like insulating compound. The magnetic casing provided a path for the leakage flux and thereby tended to prevent an excessive flux to permeate either one of the secondaries when the lamp connected to the other secondary was not functioning.

In Figure 21 have illustrated another transformer which is like the transformer of Figure 1, differing therefrom only in that a greater amount of space is provided between the primary coil 1 and the secondary coil l0 and between the primary coil 8 and the secondary coil ll. A'magnetic shunt 30 is provided in that space said shunt contacting one leg of the transformer and being spaced from the other leg of the transformer by a short non-magnetic gap 3! which may be of a length of the order of .01 inch to .03 inch. This gap may be fllled with a sheet of paper or other non-magnetic material. In the event that the lamp which is connected to one of the secondary coils should be out of order the magnetic shunt 30 provides a path for flux permeating the primaries '|--9 and prevents saturation of the portion of the transformer core where the two secondaries are located. The wiring connections for the transformer of Figure 2 are the same as for Figure 1.

In Figure 3 I have shown an alternate arrangement wherein the transformer is provided with four primaries and two secondaries connected identically the same as in the circuit of Figure 1. This transformer is provided with two additional coils 3536 each of which has only a few turns. The coil 35 surrounds the coil 6 and the coil 38 surrounds the coil 8. The two coils 35-38 are connected in series with one another and are connected in series with the secondary coil Ill. The direction of the turns in the coils 35-3B is such that the voltage generated therein tends to buck the voltage generated in the coil l0. As a result, if there is any tendency for the'current to rise in the coil Hi the bucking effect of the coils 3H8 manifests itself to av degree which increases as the current rises, thereby limiting the rise of the current to very small values.

In compliance with the requirements of the patent statutes I have here shown and described 4 a few preferred embodiments of my invention. It is, however, to be understood that the invention is not limited to the precise constructions here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent is:

1. A transformer for supplying electrically displaced currents for operating a plurality of glow discharge tubes having negative resistance characteristics comprising a core having two opposite side legs connected in a magnetic circuit, a pair of primary coils on each leg, at secondary on each leg between the two primaries on the same leg, the four primary cells being connected in series, each of the secondaries being connected to the primaries in step-up auto transformer arrangement, each secondary having leads for connecting it to one of the tubes, a condenser in series with one of the secondaries for causing it to furnish a leading current, and means for preventing saturation of the portion of the core between two adjacent primary coils that are on opposite legs of the transformer, said last-named means being on only one side of the secondaries.

2. A transformer for supplying electrically displaced'currents for operating a plurality of glow discharge tubes having negative resistance characteristics comprising a core having two opposite side legs connected in a magnetic circuit, a pair of primary coils on each leg, a secondary on each leg between the two primaries on the same leg, the four primary coils being connected in series, each of the secondaries being connected to the primaries in step-up auto transformer arrangement, each secondary having leads for connecting it to one of the tubes, a condenser in series with one of the secondaries for causing it to furnish a leading current, and means for preventing saturation of the portion of the core between two adjacent primary coils that are on opposite legs of the transformer, said last-named means being on only one side of the secondaries, the two primary coils on each leg of the transformer being spaced apart a distance at least as great as the combined lengths of the two primary coils.

3. A transformer for operating a plurality of glow discharge tubes comprising a core having two opposite side legs connected in a magnetic circuit, a pair of primary coils on each leg, a secondary on each leg between the two primaries on the same leg, the four primary coils being connected in series, each of the secondaries being connected to the primaries in step-up auto transformer arrangement, each secondary having means for connecting it to one of the tubes, and means for preventing saturation of the portion of the core between two adjacent primary coils that are on opposite legs of the transformer, said last named means comprising an auxiliary coil on the transformer core in series with one of the secondaries but in opposition thereto.

4. A transformer for supplying electrically displaced currents for operating a plurality of glow discharge tubes having negative resistance characteristics comprising a core having two opposite side legs connected in a magnetic circuit, a pair of primary coils on each leg, a secondary on each leg between the two primaries on the same leg, the four primary coils being connected in series, each of the secondaries being connected to theprimaries' in step-up auto transformer arrangement, each secondary having leads for connecting it to one of the tubes, the two primary legs of the transformer, the shunt being on only one side of the secondary coils and having an air gap therein.

5. A transformer for operating a plurality of glow discharge tubes comprising a core having two opposite side legs connected in a magnetic circuit. a pair of primary coils on each leg, a secondary on each leg between the two primaries on the same leg, the four primary coils being connected in series, each of the secondaries being connected to the primaries in step-up auto transformer arrangement, and each secondary having means for connecting it to one of the tubes, a condenser in series with one of the secondary coils, and an auxiliary coil in series with the other secondary coil and in opposition thereto, said auxiliary coil having less than of the number of turns on said other secondary coil and having closer coupling with one of the primary coils than does said other secondary coil.

8. A transformer for operating a plurality of glow discharge tubes comprising a core having two opposite side legs connected in .a magnetic circuit, a pair of primary coils on each leg, a secondary on each leg between the two primaries on the same leg, the four primary coils being connected in series, each of the secondaries being connected to the primaries in step-up auto transformer arrangement, and each secondary having means for connecting it to one of the tubes, the two primary coils on each leg of the transformer being spaced apart a distance at least as great as the combinedlengths of the two primary coils, and means for preventing advance 6 saturation of the portion of the core between two adjacent primary coils that are on opposite legs of the transformer, said means comprising an auxiliary coil in series with one of the secondary coils and in opposition thereto, said auxiliary coil being concentric with said two last mentioned primary coils.

7. A transformer for operating a plurality of glow discharge tubes comprising'a core having two opposite side legs connected in a magnetic circuit, a pair of primary coils on each leg, a secondary on each leg between the two primaries on the same leg, the four primary coils being connected'in series, each of the secondaries being connected to the primaries in step-up auto transformer arrangement, and each secondary having means for connecting it to one of the tubes, the two primary coils on each leg of the transformer being spaced apart a distance at least as great as the combined lengths of the two primary coils. and means for preventing saturation of the portion of the core between two adjacent primary coils that are on opposite legs of the transformer, said means comprising an auxiliary coil in series with one of the secondary coils and in opposition thereto, said auxiliary coil being concentric with said two last mentioned primary coils, and a condenser in series with the other one of said two secondaries.

PAUL BERGER.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,950,395 Boucher Mar. 13, 1934 2,292,923 Boucher Aug. 11, 1942 40 2,382,638 Keiser et a1 Aug. 14, 1945 

